1. Field of the Invention
The invention relates to increased heat exchange in a two or three phase, liquid continuous slurry that contains gas bubbles. More particularly, the invention relates to increasing indirect heat transfer into or out of a liquid continuous, two or three phase slurry in a vessel, by using ribbed tube heat exchangers, in which the ribs are aligned generally along the longitudinal axis of the tubes and parallel to the overall flow direction of the gas bubbles, with the aspect ratio of the ribs less than 5 and with the ratio of the base tube O.D. to the rib height greater than 10. This is useful for increasing the productivity of a slurry Fischer-Tropsch hydrocarbon synthesis reactor.
2. Background of the Invention
Chemical processes occurring in two or three phase slurries comprising a slurry liquid in which is dispersed or suspended (i) gas bubbles or (ii) gas bubbles and particulate solids are known and find use in a variety of applications, including conversion reactions in which a reactant is reacted with a hydrocarbonaceous or other feed, to convert the molecular structure of at least a portion of the feed. These reactions are typically conducted in the presence of a catalyst. Such reactors are sometimes referred to as ebulating bed reactors in which the upflowing gas and or liquid serve to expand and disperse the particulate solids which can comprises either part of the feed (e.g., coal liquefaction), the catalyst or other particles for various reactions. This includes slurry hydrocarbon synthesis reactions, in which bubbles of hydrogen and carbon monoxide react in the presence of a Fischer-Tropsch catalyst in a hydrocarbon slurry liquid, to form hydrocarbons. In such applications, heat transfer limitations between the slurry and indirect heat exchange means for removing or adding heat to the slurry in the reactor, can reduce the efficiency of the reaction and limit the reactor production at a given temperature. For example, the Fischer-Tropsch hydrocarbon synthesis reaction is highly exothermic. This can limit hydrocarbon production at a given temperature, due to heat transfer limitations between the slurry and the indirect heat exchange cooling means immersed in it, inside the reactor. Such heat transfer means are typically finned or bare steam tubes, in which the cooling water flowing through them is converted into steam, as the means for removing heat from the slurry during the reaction.